Structural Stability and Electronic Structures of a Curved Graphene Sheet on Stepped SiC(0001) Surface

The structural stabilities and electronic structures of graphene sheets laid on stepped SiC(0001) surfaces are theoretically investigated by density functional theory calculations. To precisely estimate the van der Waals (vdW) binding energy between graphene sheets and SiC surfaces, the vdW density functional (vdW-DF) was used. We have found that a graphene sheet put over a stepped SiC surface has a curved structure bridging the upper and lower terraces without making any bonds to the atoms of the step. This bridging curved structure of the graphene sheet is mainly stabilized by the vdW attraction force. With respect to the electronic structure, the original sp(2) network is maintained in the curved graphene sheet. By comparing the local density of states (LDOS) of carbon atoms in the curved graphene sheet, we also found that the electronic structure of each carbon atom largely depends on the distance between the carbon atom and the surface.